The present invention relates to injector loaded from collecting chamber and provided with cascade-shaped control device.
Fuel injection systems which are designed with high pressure collection chambers (common rail) must satisfy in addition to the requirements such as longevity and favorable manufacturing costs, also the requirements of accurate dosing of the injection quantity as well as maintaining of a constant injection pressure for all injectors at all times. Injection pressure and injection quantity must be determined for each operational pressure and each injection quantity of the internal combustion engine independently from one another, so that for the mixture formation and additional freedom decree is provided. The injection quantity at the beginning of the injection must be as small as possible, to take into account the injection delay up to complete formation of the flame front in the combustion chamber of the internal combustion engine. In high pressure collecting chambers (common rail) pressure fluctuations occur due to the pump supply and injection process, and are damped by the storage volume.
U.S. Pat. No. 5,628,293 deals with an electronically controlled fuel injection with a fluid collecting chamber which is loaded by a pre-injection and has a directly controllable element for releasing the connecting line between the fluid collecting chamber and the injection nozzle which extends into the combustion chamber of an internal combustion engine. In addition to the first directly controllable injection element, a further pressure control element is reciprocatingly movable between two adjusting positions. With the both switchable pressure control elements, hydraulic forces which are opposed to one another are balanced.
In this configuration from the prior art, there is a disadvantage that the control of the pressure elements is performed by two units which, in the case of failure of the control device, can only partially secure against overpressure or an adjustable overquantity.
German patent document DE 198 35 494 A1 discloses a pump-nozzle unit. It serves for fuel supply in a combustion chamber of the direct injection internal combustion engine. It includes a pump unit for forming an injection pressure and for injection of the fuel via an injection nozzle into the combustion chamber. Furthermore, a control unit is provided, which acts on a control valve formed as an outwardly open A-valve. Moreover, a valve actuation unit is provided for controlling the pressure buildup in the pump unit. For providing a pump-nozzle unit with a control unit which has a simple construction, is small and has especially short response time, it is proposed in this reference to form the valve actuating unit as a piezoelectric actuator.
The European patent document EP 0 657 642 A2 deals with a fuel injection device for internal combustion engines. The fuel injection device disclosed in this document has a high pressure collecting chamber which is fillable by fuel pressure pump, and from which high pressure lines extend to individual injection valves. In the individual high pressure lines, control valves for controlling the high pressure injection valves as well as an additional pressure storage chamber between these control valves and the pressure collecting chamber are provided. In order to avoid application of the high system pressure continuously on the injection valves, the control valve is formed so that during the injection pauses at the injection valve its connection to the pressure storage chamber is closed and the connection between the injection valve and release chamber is controlled.
Accordingly, it is an object of the present invention to provide an injector loaded from collecting chamber and provided with a cascade-shaped control device, which avoids the disadvantages of the prior art.
In keeping with these objects and with others which will become apparent hereinafter, one feature of present invention resides, briefly stated, in a injector loaded from a collecting chamber and provided with a cascade-shaped control device, which has means forming a control chamber; a valve body which is pressure loaded from said control chamber; means forming a further control chamber; a nozzle needle which is pressure loaded from said further control chamber; a nozzle inlet; a nozzle chamber provided for said nozzle needle and loaded from said nozzle inlet; a valve body formed as a 3/2-way valve for pressure controlling the injector; a 2/2-way valve for stroke controlling of the injector at a leakage oil side; and a common controller, said valves being controllable either by said common controller or separately from one another.
With the inventive solution, an injector for injecting fuel under high pressure into the combustion chambers of an internal combustion engine is provided, in which with one controller simultaneously two servo valves are actuated and thereby a stroke-/pressure control injector is provided. By means of a pressure member which is common for both closure elements, both the valve body inside of the injector is controlled, and also simultaneously the outlet throttle of a control chamber above a stroke part of the injector is relieved. The thereby released inlet from the high pressure collecting chamber (common rail) loads both the nozzle chamber which directly surrounds the nozzle needle in the region of a pressure stage, and simultaneously the further control chamber which is located above the nozzle needle. It is loaded during controlling the inlet from the high pressure collecting chambers so that, high pressure from the high pressure collecting chamber is provided at the nozzle needle chamber. Due to the direct coupling of the both systems, namely a pressure-controlled and a stroke-controlled system, two principles inside the injector are coupled, which allow a pressure and a stroke-controlled injection process.
With the present invention an injection process which is approximately ideal for a utility vehicle is provided. During the pressure raise flank at the injector, a pressure-controlled injector is required to make available fast the required high pressure at the injection opening, while during the closing process and for a post-injection in the combustion chamber of an internal combustion engine a stroke-control led system is used so as to supply an injection nozzle for a fast relieve of the nozzle-chamber. With the inventive coupling of the both pistons of a 3/2-way valve and a 2/2-way control-valve, both control principles can be used in an injector. During the pressure buildup phase a pressure control takes place, while during the closing process and the post-injection a stroke control of the inventive injector can be performed.
In accordance with a further embodiment of the present invention, with a combination of a 3/2-way valve and a 2/2-way valve, pressure side and leakage oil side of an injector can be separated from one another. Also, with such an injector for injection of fuel during high pressure in the combustion chambers of an internal combustion engine, it can operate so that a pressure control and a stroke control of the injector can be realized during various injection phases. The pressure buildup in this embodiment is performed through a valve provided at the leakage oil side. With this injection configuration, during fully open control part the system can be controlled and during partially open control part a stroke control can be performed. Also a post-injection can be realized which can be performed at high pressure for optimizing the course of the combustion process.
The both embodiments of the inventive injector configuration allow the use of two control principles, whose advantages during the pressure buildup and during the closing process or a post-injection can be combined with one another, to satisfy the requirements of the injection characteristics, for example in utility vehicles, in an improved way.
The novel features which are considered as characteristic for the present invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.